Metal working lubricants



nite =1 METAL WORKING LUBRICANTS Thomas E. Reamer, El Cerrito, Calif., assignor to Shell This invention relates to aqueous base metal-working lubricating compositions. More particularly, it relates to a water-base metal cutting fluid.

It is well known in the art that water base fluids possess good cooling properties for processing metals, but that they lack the lubricity and extreme pressure properties of oil base lubricants and usually cause corrosion. On the other hand, oil base lubricants are inferior coolants and are costly.

The art discloses various means of imparting rust inhibiting and extreme pressure properties to water base metal-working lubricants, but with littlesuccess. Among the materials commonly used for this purpose are watersoluble non-ionic compounds, such as alkyl phenolethylene oxide reaction products, talloW, fatty acids, soaps, such as sodium or potassium oleate or sulfonate, in combination with water-soluble alkali metal compounds and mixtures thereof, such as the nitrites, phosphates, carbonates, or chromates, e.g., mixtures of sodium nitrite and sodium phosphate, or mixtures of sodium nitrite and sodium carbonate. Water-oil emulsions additionally present a dermatitis and stability problem upon use and are generally undesirable because of their opaqueness thus making it diflicult to observe the machining process.

It is an object of this invention to provide a cutting fluid having both good cooling and good lubricating properties. Another object of the invention is to provide a non-corrosive aqueous cutting solution. Still another object of the invention is to provide a stable, non-corro sive, aqueous cutting composition free of ingredients capable of causing dermatitis infections. Another object of the invention is to provide a multi-functional metal working lubricant useful at high speeds, heavy loads, high pressures and high temperatures.

The above and other objects are attained in accordance with the present inventionby an aqueous medium, such as water containing from about 0.5% to about 15%,

preferably from 2% to 10% by weight each of (1) a water-soluble normal alkali metal salt of apolymercapto- (thin-)carboxylic acid having the general formula R(S R -COOH) wherein R. and R, can be the same or different alkylenegroups of from 1 to 6 and preferably from 1 to 4 carbonatoms such as methylene, ethylene or .butylene groups, x is an integer of from 2 to 4, and y is an integer of 1 to 2; (2) an alkanolamine, such as'mono dior triethanolamine, mono-, di-, or'tripropanolamine,

etc., or the like; and (3) a water-soluble hetero copoly- -.meric alkylene'glycol, etheror ester thereof, wherein the different oxyalkylene units are substantially"randomly the alkanolamines inhibit corrosion without producing .any undesirable sideclfectaiwhich is no nne of alkali States Patent f Patented Apr. 25, 1961 metal nitrites which form unstable solutions in combination with polymercaptocarboxylates. The water-soluble hetero copolymerimproves the antifrictional properties of compositions of the present invention, particularly under slow sliding conditions. On the other hand, other nonionic polymeric compounds such as alkyl phenol-ethylene oxide reaction products, block copolymers of dissimilar alkylene oxides and their derivatives such as are commercially available under the trade name of Pluronics and the like produce undesirable frictional problems, foaming, instability and the like.

The alkylene polymercaptoearboxylic acids'are prepared by reacting an aliphatic mercapto carboxylic acid with an aliphatic carbonyl compound such as an aliphatic aldehyde. Methods of preparing such acids are described by Ritter et al., JACS 74, 5576 (1952), or Holmberg et al., Ann 353, 123 (1907). Among the mercapto acids are included mercaptoacetic acid, alpha or beta-mercaptopropionic acids, alpha,beta-dimercaptopropionic acid, alpha-mercaptobutyric acid and the like. The organic carbonyl compounds include aldehydes such as formaldehyde, acetaldehyde, butyraldehyde, glyoxal, or ketones such as acetone, butanone, etc.

The water-soluble neutral polyalkali metal salts of an alkylene polymercaptocarboxylic acid include dior tetrasodium, lithium or potassium salt of methylene bis(mercaptoacetic acid), ethylene bis (mercaptoacetic acid), methylene bis(mercaptopropionic acid), methylene bis- (mercapto acid), methyl bis(mercaptoacetic acid),

ethylene tetrakis(mercaptoacetic acid), ethylene tetrakisratios of from 75:25 to 10:90 ethylene oxide to 1,2-pr0- pylene oxide, and molecular weight from about 250 to about 1500.

By a ratio of from 75 :25 to 10:90 is meant that, in the formation of copolymer the amount of 1,2-propylene oxide is from /3 to 9 times the amount of ethylene oxide present, byweight, the parts or proportion of the 1,2-propylene oxide being given last.

' scribed in U.S.'Patents 2,425,755 and 2,425,845. The copolymer diols may be employed in a modified form as the monoethers ormonoesters of monohydric alcohols or atoms.

:inpercentages by weight.

Disodium monobasic acids the diols. The alcohols preferably have from 1 to about 10 carbon atoms, while the monocarboxylic acids preferably have from i to 12 carbon The alkanolamines which are used in compositions of this invention include mono, di-' and tri-ethanolamine, propanolamine, N,N-dimethylisopropanolamine, and mixtures thereof; Y

The following compositions are representative of the invention, which can be useineat or diluted with from lto 10 partsof'water, as metal-working lubricants for cutting,drilling-and thelike. {The proportions are given methylene bis(mercaptoacet ate) Hetero-copolymer of ethylene, oxide -l, 2-propylene oxide (75725 having a viscosity ,of at These materials are de- Composition B Composition C Disodium salt of methylene bis(dimercaptoacetic acid) 6 Hetero-copolymer of ethylene oxide-1,2-propylene oxide (75/25) having a viscosity of 1400 at 100 F. Dimethylisopropanolamine 2 Sodium mercaptobenzothiazole 0.1 Water Balance Composition D Tetrapotassium salt of ethylene tetral;is(mercaptoacetic acid) 4 Hetero-copolymer of ethylene oxide-1,2-propylene oxide (75/25), having a viscosity of 1400 at 100 F. Diethanolamine 4 Sodium mercaptobenzothiazole 1 Dimethyl silicone polymer 0.001 Water Balance Composition E Dipotassium salt of methylene bis(mercaptoacetic acid) 2 Hetero-copolymer of ethylene oxide-1,2-propylene oxide (75/25) having a viscosity of 450 at Triethanolamine 2 Water Balance The outstanding properties of compositions of this invention are demonstrated by results obtained from subjecting them to the following tests:

(1) Four-ball machine tests as described in the Journal of the Institute of Petroleum Technology, pages 7 206-229, April 1946.

(2) Drilling test: The compositions were used in drilling deep 1" holes in A151 4340 steel at 1440 rpm. and

compared with a reference waterbasecu tting fluid (X), the reference fluid being rated as 100%.

' Compositions A-E in the four-ball test gave average weld loads of between 600 and 1000 kg., and these compositions gave values of from 300 to 800% above the reference fluid (X). The substitution of other salts of sulfur-containingcarboxylic acids for the polyalkali metal mercap'topolycarboxyla'tes used in compositions of this invention such as sodium mercaptoacetate or sodium dibutyldithiocarbamate gave much lower weld'loads in the four-ball machine, around 200300. Also, the substitutionof other types of non-ionic compounds for the heterocopolymer used in'Compositions A -E, such as a .block copolymer of ethylene oxideand propylene oxide available commercially under the trade name Pluronic L64 (Wyandotte Chemical Company) or an alkylphenolethyleneoxide' condensation product, caused excessive foaming, whereas compositions (A-E) of the present invention are non-foaming.

Compositions of this invention may contain additional additives, such as water-soluble corrosion inhibitor," e.g., sodium mercapto benzothiazole, anti-foaming agents such as silicone polymer, 'perfuming agents, and dyes. The

4 this invention have good surface finish, are free from rust and the cutting tool life is excellent.

I claim as my invention:

1. An aqueous metal-working lubricant comprising a major amount of water and from about 0.5% to 15% each of (1) a water-soluble normal alkali metal salt of an alkylene poly(mercaptoalkylene carboxylic acid), said compound having from 1 to 4 carboxyl groups in the molecule and the alkylene radical being selected from the group of methylene, ethylene and butylene radicals, (2) a water-soluble hetero-copolymer of a mixture of randomly distributed ethylene and propylene oxides in the molecular ratio of from 75:25 to 10:90, respectively, having a molecular weight of from about 250 to about 1500, and (3) a water-soluble alkanolamine.

2. An aqueous metal-Working lubricant comprising a major amount of water and from about 2% to about 10% each of (1) a water-soluble neutral dialkali metal salt of an alkylene bis(mercaptoalkylene carboxylic acid), the alkylene radical being selected from the group of methylene, ethylene and butylene radicals, (2) a water-soluble hetero-copolymer of ethylene oxide and 1,2-propylene glycol in the ratios of from 75:25 to 10:90 respectively and having a molecular weight of from about 250 to about 1500 and (3) a water-soluble alkanolamine.

3. An aqueous metal-working lubricant comprising a major amount of water and from about 2% to about 10% each of (l) a water-soluble neutral tetraalkali metal salt of an alkylene tetrakis(mercaptoalkylene carboxylic acid), the alkylene radical being selected from the group of methylene, ethylene and butylene radicals, (2) a watersoluble hetero-copolymer of ethylene oxide and 1,2-propylene glycol in the ratios of from 75:25 to 10:90 respectively and having a molecular weight of from about 250 to about 1500 and (3) a water-soluble alkanolamine.

4. An aqueous metal-working lubricant comprising a major amount of water and from about 2% to about 10% each of (1) a water-soluble neutral disodium metal salt of an alkylene bis(mercaptoalkylene carboxylic acid), the alkylene radical being selected from the group of methylene, ethylene and butylene radicals, (2) a watersoluble hetero-copolymer of ethylene oxide and 1,2-propylene glycol in the ratios of from 75 :25 to 10:90: respectively and having a molecular weight of from about 250 to about 1500 and (3) a water-soluble ethanolamine.

5. An aqueous metal-working lubricant comprising a major amount of water and from about 2% to about 10% each of (1) a water-soluble neutral tetrasodium metal salt of an alkylene tetrakis(mercaptoalkylene carboxylic acid), the alkylene radical being selected from the group of methylene, ethylene and butylene radicals, (2) a water-soluble heterocopolyrner of ethylene oxide and 1,2-propylene glycol in the ratios of from 75 :25 to 10:90 respectively and having a molecular weight of from about 250 to about 1500, and (3) a water-soluble ethanolamine. p

:6. An aqueous metal-working lubricant comprising a major amount of water and from about 2% to'about 10% each of (1) disodiumsalt'of,methylene bis(mercaptoacetic acid), (2) ,a water-soluble hetero-copolymer of ethylene oxide and 1,2-propylene glycol in the ratios of from 75:25. to 10:90 respectively and having a molecular weight of from about 250 to about 1500 and (3) a watersoluble alkanolamine.

to 1% of sodium mercaptobenzothiazole;

8. An aqueous metal-working lubricant comprising a major amount ofwater and from about 2% to about 10% compositions maybe applied with excellent results to general cutting operations where cooling and lubricating of thetool an'd workpiece under adverse conditions are encountered. Metals machined with the aid of fluids of water-soluble alkanolamine: f

each of (1) tetrasodium salt of ethylene tetrakisfiner of from 75:25 to,10: respectively and having a molecular weightof from about 250 to about1500 and (3) a 3-.' aq s me al-:workingclubricarit comprising a captoacetic acid), (2) a'water-soluble hetero-copolymer of ethylene oxide and 1,2-propylen'e' glycol in theratios major amount of water and from about 2% to about 10% each of (1) dipotassium salt of methylene bis(mercaptoacetic acid), (2) a water-soluble hetero-copolymer of ethylene oxide and 1,2-propylene glycol in the ratios of from 75:25 to 10:90 respectively and having a molecular weight of from about 250 to about 1500 and (3) a watersoluble alkanolamine.

10. An aqueous metal-working lubricant comprising a major amount of water and from about 2% to about 10% each of (1) tetrapotassium salt of ethylene tetrakis(thiaacetic acid), (2) a water-soluble hetero-copolymer of ethylene oxide and 1,2-propylene glycol in the ratios of from 75:25 to 10:90 respectively and having a molecular weight of from about 250 to about 1500 and (3) a watersoluble alkanolamine.

References Cited in the file of this patent UNITED STATES PATENTS Roberts et a1. Aug. 19, 1947 Toussaint et a1. Aug. 19, 1947 Gresham et a1 Sept. 28, 1948 Gregory et a1. July 8, 1952 Beaubien et a1 Mar. 4, 1958 FOREIGN PATENTS Great Britain Oct. 6, 1954 Great Britain Jan. 5, 1955 

1. AN AQUEOUS METAL-WORKING LUBRICANT COMPRISING A MAJOR AMOUNT OF WATER AND FROM ABOUT 0.5% TO 15% EACH OF (1) A WATER-SOLUBLE NORMAL ALKALI METAL SALT OF AN ALKYLENE POLY(MERCAPTOALKYLENE CARBOXYLIC ACID), SAID COMPOUND HAVING FROM 1 TO 4 CARBOXYL GROUPS IN THE MOLECULE AND THE ALKYLENE RADICAL BEING SELECTED FROM THE GROUP OF METHYLENE, ETHYLENE AND BUTYLENE RADICALS, (2) A WATER-SOLUBLE HETERO-COPOLYMER OF MIXTURE OF RANDOMLY DISTRIBUTED ETHYLENE AND PROPYLENE OXIDES IN THE MOLECULAR RATIO OF FROM 75:25 TO 10:90, RESPECTIVELY, HAVING A MOLECULAR WEIGHT OF FROM ABOUT 250 TO ABOUT 1500, AND (3) A WATER-SOLUBLE ALKANOLAMINE. 